Method of and means for utilizing the pressure in the interior of an electric conductor carrying current.



E. F. NORTHRUP.

METHOD OF AND MEANS FOR UTILIZING THE PRESSURE IN THE INTERIOR OF AN ELECTRIC CONDUCTOR CARRYING CURRENT.

APPLICATION FILED HA3. 1, 190'."-

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METHOD OF AND MEANS FOR UTILIZING THE PRESSURE IN THE INTERIOR OF AN ELECTRIC CONDUCTOR CARRYING CURRENT.

I APPLICATION FILED MAB. 1, 1907.

Patented Oct. 27, 1908.

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E. F. NORTHRUP.

METHOD OF AND MEANS FOR UTILIZING THE PRESSURE IN THE INTERIOR OF AN ELECTRIC CONDUCTOR CARRYING CURRENT.

APILIOATION FILED MAR. 1, 1907.

Patented 0ct.-27, 1908.

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I E. F. NORTHRUP. METHOD OF AND MEANS FOR UTILIZING THE PRESSURE IN THE INTERIOR OI AN ELECTRIC CONDUCTOR CARRYING CURRENT.

APPLICATION FILED MAB-1, 1907. 902,10 Patented 0012.27, 1908.

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g vention comprises the novel method and apa citizen of the United States, residing at the device shown in Fig. 3; Fig. 3 atop plan '7 7 Fig. 6; Fig. 8', a detail side elevation UNITED STATES PATENT OFFICE.

EDWIN F. NORTHRUP, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE LEEDS AND NORTHRUP COMPANY, OF PHILADELPHIA, SYLVANIA.

PENNSYLVANIA, A CORPORATION OF PENN- ME'IHOD OF AND MEANS FOR UTILIZING THE PRESSURE IN INTERIOR OF AN ELECTRIC comano'ron Specification of Letters Patent.

CARRYING CURRENT.

Patented Oct; 27-, 1908.

Application filed March 1, 1901. Serial No. 359,983.

To all whom it may concern:

Be it known that I, EDWIN F. NORTHRUP,

Philadelphia, in the county 'of Philadelphia and -State of Pennsylvania, have invented certain new and useful Im rovement's in Methods of and Means for Uti izing the Pressure in the Interior ofan Electric Conductor Carrying Current, of which the following is a specification. i

' The primary object of this invention is the utilization of the pressure within the mass of an electric conductor, due to the passage of an electric current therethrough, to produce useful motion or workof any kind to which the force may be adapted, such for example as theoperation of motors, dynamos, electric meters and measuring instruments of various kinds and for various other purposes.

With the above objects in view my said inparatus herein described and more particularly pointed out in the accompanying claims.

In order to more fully describe my said invention, reference will be had to the accompanying drawings wherein,

Figures 1 and 2 are diagrams to illustrate the pressure on the interior of an electric conductor Fig. 3, a diagram to further illustrate the principle of my invention; Fig. 3 a fragmentary sectional view of a modification of of parts shown in Fig. 3*; Fig. 4, a vertical section partly in elevation of a motor embodying my invention; Fig. 5, a section on line 5 5 Fig. 4, looking down; Fig. 6, a bottom plan view of one of the non-magnetic conducting elements; Fig- 7 a section on line of one of the small tubes for conveying the liquid conductor from the center to the periphery of a non-magnetic element Fig. 9, 2. front elevation of one of the magnetic metal disks inserted between the non-magnetic elements Fig. 10, a vertical central section partly in elevation of an'ammeter embodymg my said invention; Fig. '11, a section-on the line 11 11 of Fig. 10; Fig. 12, a top plan view with top cover removed of a form of ammeter embodying my invention Fig. 13 a fragmentary section along the line 13 13 Fig. 12; Fi 14,- asection on line 14 l4 Fig. 12, wit the top and bottom covers, and

wire parallel to the axis of the liquid conducsmall wire the current indicating attachment in place; Fig. 15, a bottom plan view of the instrument with bottom cover removed; ig. 16, an enlarged detail fragmentary section on line -16 Fig. 15 looking in .the direction of the arrow, and Fi 17, a section on line 17 1'7' Fig. 14, o the reading attachment.

In order to make clearer the principle and operation of some specific forms of practical apparatus, embodying, my invention it will be well first to consider the physical forces which produce the pressure in the interior of a non-magnetic liquid conductor carrying an electric current and the law governing the pressure set up by these forces.

Referring to Fig. 1, let the large circle represent the periphery of a non-magnetic liquid conductor of circular cross-section, and suppose there is located in-this conductor, at

distance r from the axis a small solid conductor f. Let this small solid conductor be a tor and located at a distance r from the axis of said li uid conductor. If a current I pass through t e liquid conductor ofradius R, the f will be in a field of force of intensity If current is passing in the same direction through the liquid conductor and thewire f, the w1re will experience a force, if the current density in it is greater than the current den sity in the liquid conductor, Which will tend to move the wire across the lines of force in a direction to bring it toward and parallel to the axis of the liquid conductor.

In place, now, of an actual wire on the inside of the liquid conductor we may picture this 1i uid column as made up of a great many aments, each filament carrying a current proportional to the total current and to the cross section which we conceive any filament to have. Each filament, except the one on the axis will find itself in a field of magnetic force. Those filaments near the circumference will be in a field of greater intensity than those near the axis. Hence all the filaments, except the one on the axis, will experience a force which, if free to act, will urge them toward the axis of the conducting liquid column. The result will be that the cal ed (11".

liquid column will be under a greater hydrostatic pressure at its axis than at its circumference. We may determine the magnitude of this pressure at difierent distances from the axis by the following considerations: Let Fig. 2 represent the cross-section of a cylindrical conductor. Conceive this crosssection to be made up of a lar e number of annular spaces as l, 2 3, etc. iet the radial de th of each of these annular s aces be Let It be the radius of t e cylindrical conductor, and 1' the radial distance from the axis to any point within the circular cross-section. It should further be supposed that the conductor is of very great length, having its axis perpendicular to the plane of the paper, and far. removed from any return circuit. By the theory all portions of the conductor, as the annular sections 1, 2, 3, etc., are under the influence of a force, when the conductor is carrying a current, which tends to urge them radially toward the axis. This force, as measured in dynes, will have at any point distant 1' from the axis, a definite value per unit of area. The total force or ressure which acts upon the surface ofany imaginary cylinder of radius r and length I, will be, evidently, the force per unit of area multiplied by the total area of a length Z of this imaginary cylinder.

It is first required, to find the force, g, per unit of area, atany point within the conductor distant 1' from the axis, and second, the force or ressure P on the surface of an ima inary cy der of radius r, and axial length This problem may be solved by conceiving the action of the magnetic field on all portions of the conductor carrying current, or

by considering only the mutual attractionsof all the elements of the conductor.

By the first method, we may proceed as follows: At a point within the conductor distant r from the axis the intensity of the magnetic field is where I is the total current flowing in the conductor. The lines of force of this field are circles, having as their common axis, the axis of the conductor. Consider any single annular space as 5. It will carry current-(it, which is in the same ratio to the total current as the area of the annular s ace is to the total area of the cross section 0 the conductor. If we call da, the area of the annular space which has an inside boundary of radius 1', we have dc 1r(r clr) 111* Znrdr,

since the square. of dr can be neglected. Then, as nR is the total area, we obtain sea, me

This current, (ii, is disposed in a field of intensity If the current I flows downward, the lines of force would act on a unit north pole to move it in a clockwise direction around the axis; and an element of this conductor carrying a downward current would tend to move radially toward the axis. were reversed, the direction of the magnetic lines would be reversed but the current elements would still tend to move toward the axis. The force in dynes with which a length l of any conductor is acted upon to move at right angles to the lines of magnetic force is, in electro-magnetic measure, numerically equal to the product of the length of the conductor, to the strength of the current in the conductor and to the field intensity where the conductor is located. (MaxwellVol. II M90.) Thus calling (IF the force with which the element carrying the current (it tends to move radially toward the axis, we have It should be noted that the force, dF, is distributed so as to act normally on a surface the area of which is 27rd. Hence calling dg the force per unit of area, or the force intensity acting radially inward, we have This is the intensity of the pressure at distance r from the axis, due to the current in a single annular space of radial depth (11'. .l t is necessary in order to obtain the total intensity, g, at the distance r from the axis, to take the sum of the force intensities due to the currents in all the annular spaces, each of radial depth (11', which lie in the space included between the radius R and the radius 'r. This sum is given by the integral Performing the integration, we have Equation (5) gives the inward radial ressure per unit of area on the material 0 the conductor itself at any distance r from the axis of the conductor. If I is the current per unit of cross-section, or the current density in the conductor, I =I, 1r R and we obtain as another expression for the pressure If the direction of the current The pressure at the center, where r.- O, is therefore equal to the area of the cross-section of the conductor multiplied by the square of the current density. The total pressure on the surface of an imaginary cylinder of length Z and radius 1' is, evidently, the force per unit of area multiplied by the ,total area of the surface of the cylinder considered.

' Calling P this pressure, We have:

These same expressions are easily obtained by conceiving the imaginary conducting shells to exert an attraction according to the law of mutual attraction between currents flowing parallel and in the same direction. The laW of attraction between any two infinitely long parallel conductors distant r from each other and carrying currents i and I Here Z is the portion considered of the length (See Maxwell uniform current density beingsu posed.

21rrdr is, as previously fou'n the crosssection of the annular area and the current which it carries is therefore i at (10 The current 'i and (Z11 attract and produce a pressure over the surface of the cylinder of radius r. Calling dF this pressure, we have The pressure per unit of area is: 4

dF 2I rdr' 57F vrR whence, in integrating, we obtain and These'last two expressions are seen to be identical with (5') and (7).

Attraction in the interior of a conductor.

The attraction in the interior of a cylindrical conductor carrying I units of current per unit of cross-section which would be exerted upon a unit length of a unit of current distant 1' from the axis, may be found as follows:

In equation'(9) let Z; 1, and we have The current carried by the conductor of radius r is which combined with the above gives 27W: I F calling I the current per unit of cross-section of the conductorand taking-i equal to unity, We find Equation (13 expresses the attraction in the interior of a conductor carrying current. It is analogous to the gravitational attrac- .tion in the interior of a body of the same form as the conductor, due to its mass only.

Having thus determined, it is believed for the first tlme, the law of the hydrostatic pres sure existing in the mass of a conductor of circular cross-section carrying an electric current, a reference to Fig. 3, will further illustrate and prove the said law. Referring to said figure, 9 represents a tube of insulating material of 2.54 C. M. interior diameter'and 10 another tube of insulating material of about 4 C. M. inside diameter; 11 and 12, plugs of brass or copper inserted in the ends of tube 9; 13 and 14 copper terminals to be connected to a sourceof current, 15 a plug of fiber or other insulating material inserted in tube 9 about midway of the length of said tube, and having a vertical opening 1 6 through its center of a radius of .635 C. M: Through the sides of the tube 9 and plug 15 are openings '17 which pass into the central 1 opening 16. The openings 17 in the appara tus constructed had an inside diameter of 3.2 MM. The bottom of the space between the tubes 9 and 10 is closed by a ring of insulating material 18, 19 indicates mercury and'20' a hole or passage through plug 12 to permit the mercury to flow from the tube 9 into tube 10...

According to the theory herein given when current is passed through the mercury column in the tube 9 a hydrostatic pressure should be produced along the axis of the column of mercury. Hence as the mercury has no other escape than the hole 20 provided in the brass lug 12, it should rise in this hole, being at t ie same time drawn in at the holes 17. Sufiicient pressure should raise the mercury in the hole 20 until it overflows the upper surface of the plug 12 and falls back into the tube 10, from whence it came. Thus a continuous stream of mercury should flow by the path, through the holes 17, up the tube 9 and the hole 20 into the tube 10 and thence again to the holes 17 When sufficient current was used these results were amply realized, the mercury flowing in a rapid stream as described. It was found, however, that the same ressure may be obtained with amuch sma er current if within the plug 15 is inserted a small soft lron plug 21 (see Figs. 35 and 3 provided with a slot to register with opening 17. The reason for this is the greatly increased intensity of the magnetic field in the slot 22 due to the iron. The conducting mercury 'filaments in the slot are therefore urged with increased force towards the axis of the tube 9 and the hydrostatic pressure at the axis is likewise increased.

Based upon the foregoing theory I have devised several forms of apparatus for the conversion of the pressure in the mass of the liquid conductor into useful results.

In Figs. 4 to 9 I have shown the principle embodied in an electric motor wherein there is a continuously moving element-a rotary body in the case shown. In said figures, 23 and 24 indicate conductor heads preferably of copper having terminus 25 and 26 for connection to a source of current. The head 23 is provided with a cylindrical chamber 27 opening through the bottom of said head and through the side as at 29. The head 24 has a smaller vertical chamber 30 opening through the bottom, and a horizontal passage 31, passing entirely through its upper portion and opening-into chamber 30. ne end of assage 31 is closed by means of a screw p ug 32, of insulating material while into the other end of said passage passes a The other tube 33 of insulating material. end of said tube asses into the opening 29, the said tube fil ing both of sai openings Within the tube 33 is mounted a propeller screw 28, carried on a shaft 34 connected at one end as at 35 and at its other end passing through plug 32 and stuffing box 36 on said plug. The shaft 34 may carry a pulley 37, or may be connected in any other esired way to the apparatus it is intended to operate.

Secured to the heads 23 and 24 res ectively' are two cylindrical members 38 anc 39 each of which is built up of a series of non-mag netic conductor elements 40, soft iron disks 41 inserted between said elements, and metal.

tightly v a desire rings 42. The elements are screw threaded externally, as at 43 and 44 and these engage interior screw threads on the rings 42 of high resistance metal. Each of said elements 40 is also recessed as at 45 (see Figs. 6 and 7) and in each of said recesses is mounted a small tube 46 of insulating material leading from a point at the center of the top of the element to a point near the periphery thereof.

Each disk 41 is provided with a slot 47 (see Figs. 5 and 9) which communicates with tubes 46 both above and below. Annular flanges 48 are provided on the elements 40 to radiate the heat.

The lowermost rings 42 screw into projec tions 49 and 50 on a conducting base 51 preferably of copper. The base 51 is provided with a vertical chamber 52 which registers with the center'of disk 41 on the left, and with a vertical chamber 53 which opens into the slot in disk 41 on the right near the eriphery of said disk. The chambers 52 and 53 open into a horizontal chamber 54 closed at one end by the metal of the base 51 and at the other by a plug 55 driven thereinto. The chambers 52 and 53 are lined with insulating tubing 56 and the chamber 54 with similar tubing 57. The lining of these chambers may be omitted.

46 represents insulating cement packing to prevent leakage of the liquid conductor past tubes 46.

The plug 32 is removed and mercury 53 or other suitable liquid conductor is poured into chamber 30 passing down through the various elements of member 39 as shown, thence u through member 38 until it reaches level 59 in chamber 27. If desired oil 60 may be put on top of the column of mercury in the chamber 27 for lubricating the bearing 35 and breaking up the mercury stream from the propeller as it falls into the chamber 27, thus preventing a short circuit. The mercury is further broken up by the holes 60 in a small insulating disk 60 in t 1e column 27.

When the terminals 25 and 26 are 0011110 ted to a source of current, alternating or direct, current will pass say from terminal 25 through the member 38 base 51, member 39 thence to terminal 26.

In accordance with the theory above set forth the mercury at the center of said elements will be under a greater hydrostatic ressure due to the current passing through it than at the periphery of said elements, hence the mercury is forced from chamber 27 downward through the tube opening into the axis of the column of mercury in chamber 27, thence from said tube to a point of lower pressure near the periphery of the neXt element 40. The pressure towards the axis of the disk 41, next beneath said element will force the li uid to the axis of said disk, whence it w' pass into the next tube 46 below said disk and so on around to chamber 30, whence the liquid passes under the combined pressures of theseveral su e posed couples or .elements until it is forced the screw 28. The mercury thus rotates the screw 28 and passes along tube 33 into chamber 27 again. The screw 28 may thus continue to rotateas long as current passes through the a paratus as described. The rotation of sai screw-imparts through the shaft '34 rotation to pulley 37, which may be connected to any desired piece of apparatus.

Inlay use in the place of mercury a liquid alloy of metallic odium and potassium, or any other suitable liquid conductor.

By adding the several pressures in series as described considerable power may be-obtained. It should also be noted that the hydrostatic ressure obtained is independent of the axial liangth of the liquid strata, while the heat developed by the current is directly as this-length. With this consideration in mind, the axiallength of the liquid portions of the apparatus from which the ressure is derived may be extremely small. y lessening these axial lengths the eificiency of the apparatus isnot lessened, and greatly im roved.

With a i uid conductor one half inch in. diameter an one thousand cells or conductor sections of say one MM length each and with a current of six hundred amperes, a ressure of 43.2 poundsper s uare inch coul be obtained, and this wit out iron in thercircuit. This pressure would sustain a column of mer cury over seven feet high. A much greater pressure with the same amount of current could be obtained with the iron disks between the successive sections of mercury hereinbefore described.

The above described apparatus isonly one of many ways of utilizing the pressure on the cool running is interior" of a conductor to produce motive power. This force which dcipends only on thesquare of the current an linear d1mensions may be used as an accurate measure of the current, either direct or alternating. With this in view ihave devised several forms of ammeters two of= which I have shown in this application.

One form of ammeter constructed accord- 7 ing to my invention is shown in Figs. 10. and

11. This instrument comprises among other parts two cylindrical member-s61 and 62 each builtup of a series of superposed elements consisting of copper or other non magnetic metal disks 63 screw threaded exteriorly on each side of an annular heat dis sipating flange 64, the said elements bein held rigidly by interiorly screw threads rings 65 preferably of some suitable high re- 'sistance'metal, there being left between the successive elements 63 a space 66 to be filled with the liquid conductor. Passing through r against tube. Passing through the top of t thec 'each of said elements a slanting direction from the one face at a point coincident with is an opening 67 lined with insu ating tubing 68. The elements in the member 61 are arranged one above the other so that,the openlngs therethrough which merge at the axes of the elements will be on top while the open ings at the periphery will be at the bottom of the element. In the member 62 this condition is reversed as will be observed from the drawings. The uppermost rings 65 of the members 61 and 62 receive the lower ends respectively of two metallic conducting plugs 69 and 70 of copper or other suitable material, the said plugs being screw-threaded into the said rings as shown. 'The plugs 69 and 70 are provided with chambers 71 and 72 respectively, which chambers communicate by means of openings 73 and 74 respectively with spaces 75and 76 above the uppermost elements of the members 61 and 62. Theplu s 69 and 70 are screw threaded res ective y into heavy terminals 77 and78 w 'ch may be of copper or other suitable material. Screw threaded on the up er portion of the plug 69 is a short tube 79 w ll a cap 80 adapted to close the top of said 1is cap 80 down into theinterior of tube 69 is a milled screw 81, the function of which is to regulate the normal height of the liquid in the indicating tube as hereinbefore described. Screwed onto the top ofthe plugl70 is a short tube 82 ich is fitted with he lowermost rings 65 of the members 61 and 62 are screw threaded onto the projections 89 and 90 on the upper face of a conducting yoke 91 of copper or other suitable low resistance metal, said extensions 89 and 90 being separated from the lowermost elements 63 bye spaces 92 and 93 respectively. The space 92 communicates with the space 93 through the chamber 94 in. the yoke 91. 95 re resents the plu for closing one end of Eambcr 94. 96 lndicates the liquid conductor which occupies all oi the spaces 66, 7 5,

.76, the interior of tube 68, spaces 92, and 93 and chamber'94. Rising normally to a suitable level in the tubes 79 and 82 as indicated.

This liquid conductor may consist of mercur or any other suitable material as stated wit res ect to the apparatus hereinbefore described. Above the mercur or other conductor 96 in the tube 82 is p aced a suitable colored liquid 97 which extends up a considerable distance in the tube 85 normally to the zero point on said scale.

By applying an electric current to the terminals 77 and 78 an internal pressure is set up in the mass of conductor 96 which acts to force the said conductor from points in line with the axes of the members 61 and 62 outwardly toward the periphery of said members. the pressures between the successive elements 63 being added one to the other as hereinbefore described and forcing the liquid conductor 96 in the plug 72 upward against the colored liquid 97 causing the lat ter to rise in the glass tube 85. As the height to which said liquid will rise in said tube is pro ortional to the square of the current the sca e 86 may readily be calibrated in amperes. The liquid in the vertical tube 85 may be adjusted to zero before the measurement is made b adjusting the screw 81.

It wi 1 be readily observed that the cylindrical members 38 and 39 of the apparatus as shown in Fig. 4 may be substituted for the members 61 and 62 of the form of apparatus just described. In case the said substitution, however, is made, the soft iron disks in the apparatus shown in Fig. 4 should be omitted. It will also be obvious that the members 61 and 62 of the apparatus shown in Fig. 10 may be substituted for the members 38 and 39 in the apparatus shown in Fig. 4.

Another form of ammeter constructed in accordance with the principles of my present invention is shown in Figs. 12 to 17 inclusive, in which 98 and 99 represent two blocks of hard wood or other suitable insulating material placed face to face and held together rigidly; 100, 101, cylindrical plugs of copper or other suitable low resistance conducting material passing through said blocks and registering with each other as indicated, the superposed plugs being separated from each other by a small space 102 (see Fig. 16); and 103 small tubes of insulating material extending from a point in the aXes of one pair of said superposed lugs to a point at or near the periphery oi an adjacent pair of said plugs, the said plugs being provided with a small groove 104 to receive said tubes. Extending axially through the upper plugs 100 on the extreme left are openings 105 and 106 respectively which are screw threaded interiorly and receive respectively two receptacles 107, and 108, the former eing rovided with a ca 109, while the top of the atter receptacle is closed by means of'a plug 110 through the axis of which passes an o ening 1 11 in which is inserted a small glass tu e 1 12 which may be extended upward to a desired height. Adjacent to this tube 112 is located a vertical scale 113, and inclosing said scale and tube isia vertical tube 114. The plugs 100, 101 are connected in series by means of scarce metallic connecting lates 115, 116 secured to the'faces of the blocl s 98 and 99 respectively, as shown. The upper plugs 100 which carry the receptacles 107 and 108 are electrically connected to terminal plates 117 and 118 which may be provided with screw holes 1 19 for attaching current terminals.

The plugs and connecting plates may be protected from ossible contact with outside conductors y means of plates of insulation 120, 121.

122 indicates the mercury or other li uid conductor, the internal pressure of whic is to be utilized, and 123 a suitable colored liquid preferably of lower density placed in the receptacle 108 above the mercury to extend up into the tube 111. 7 It will be observed that tubes 103 pass from a point of maximum pressure at the center of the liquid conductor between superposed plugs, to a point of minimum pressure, at the periphery of the next liquid conductor between superposed plugs, therefore when current is applied at the'terminals of this instrument the hydrostatic pressures produced at the axes of the liquid conducting material between superposed plugs will be added in series, with the result that the liquid in reservoir 108 will be forced upward, causing the liquid in tube 112 to rise to a height dependent upon the strength of the current. By properly 113 the height of the column in tube 112 may be made to indicate the quantity of current.

Having thus I claim is 1. The method of producing motion electrically, which consists in passing an electric current through a conductor to cause internal pressure in the mass of said conductor, and causing the said pressure to act upon a body capable of motion.

2. The method of producing motion electrically which consists in passing an electric current through a conductor to cause internal pressures within the mass of said conductor, combining these pressures in series, and causing the combined force of a plurality of the same to act upon a body capable of motion. 3. An electric conductor ity of chambers containing a liquid conductor, said chambers only communicating with each other by a passage passing from a point near the center of one chamber to a oint more remote from the center of an adacent chamber.

4. An electric conductor having a plurality of chambers containing a liquid conductor and a mass of magnetic material, said chambers only communicating with each other by a passage passing from a point near the center of one chamber to a point more described my invention what calibrating the scale having a pluralremote from the center of an adjacent chamher.

5. A heterogeneous electrical conductor comprising super osed liquid and solid conducting masses avmg means to transmit ressure at or near the center of one of said iquid masses due to the passage of electric current through said, conductor, to a point of lower pressure more remote from the center of another of said liquid masses.

6. A series of solid electrical conductors, a series of masses of liquid conducting material interposed between said solid conductors, means to transmit the hydrostatic pressure due to an electric current therethrough from a point near the center of one of said liquid conducting masses to a point more remote from the center of another of said -masses, and a movable body operative by the combined action of said pressures.

7. Means to produce motion electrically comprising a heterogeneous electric conductor adapted to transmit pressure at or near the axis of said conductor due to an electric current therethrough to a point of lower pressure more remote from the axis of said conductor, and a body movbale by said pres- SUI'B.

8. An electrical measuring instrument,

comprising an electric conductor, and indi eating means operative by the difference in pressure between two points unequal distances from the aXisof said conductor, due to current therein.

9. An electrical measuring instrument, comprising a liquid electric conductor, a receptacle therefor, and indicating means operative by internal pressure within the mass of said conductor due to the passage of an electric current therethrough.

10. An electrical measuring instrument comprising an electric conductor consisting of a liquid sodium and potassium alloy,- a receptacle therefor, and indicating means op erative by internal pressure within the mass of said conductor due to the passage of an electric current therethrough.

11. An electrical measuring instrument having a plurality of chambers containing a liquid conductor, said chambers communieating with each other only by a passage passing from a point near the center of one chamber to a point more remote from the center of an adjacent chamber, and indicating means operated by the pressure in said liquid conductor due to an electric current therein.

12. The combination with a plurality of cells formed between solid masses of elec trical conducting material and opening one into the other through a duct leading from a point near the central axis of one cell to a point in the other cell nearer the periphery thereof, of a li uid electric conductor contained in said cel s and duct, electric terminals connected to the electric conductor in the respective cells, a scale, and an indicator for said scale adapted to be operated by the displacement of said liquid conductor due to the hydrostatic pressurecreated therein by the passage of an electric current therethrough.

13. The method which consists in causing an hydrostatic pressure within the mass of a liquid conductor by passing an electric current therethrough, providing for the displacement of said conductor due to said pressure,

and utilizing this displacement to measure the current.

In testimony whereof I afliX my signature in presence of two Witnesses.

EDWIN F. N ORTHRUP.

Witnesses:

FRANCIS S MAGUIRE, JOHN H. HOLT. 

